Gravel packing of wells



July 28, V1959 i' c. c. KILLIINGswoR'rH 2,895,714

4 GRAVEL PACKING oF `WELLS l 2 Sheng-sheet 1 Filed Nv. 5. 1956 i I INVENTOR.

/ @E0/L @.K/LL//vaswoRrH ATTORNEY July 28, 1959 c. c. KILLINGswoR'n-l 2,896,714

@RAVEL PACKING oF WELLS -F:'L1ed.No\r. 5. 1956 2 Sheets-Sheet 2 Mily ' 5 AINVHNTOR. GEC/l. aK/LL/NGSWORTH ATTORNEY nited States Patent GRAVEL PACKING LF WELLS Cecil C. Killingsworth, Los Angeles, Calif.

Application November 5, 1956, Serial No. 620,324

Claims. (Cl. 1'66-415) Thisv invention relates to the fluid ow method gravel packing of wells, and is particularly directedl to improvements in method andv apparatus for obtaining an improved gravel pack around' a screen pipe or perforated liner in oil wells, the gravel pack completely lling an enlarged cavity around the perforated liner or screen pipe.

Although the gravel packing ofy the well techniques have been extensively employed, and although the problem of excluding sand and other formation solids has been recognized for many years, no one, so. far as I am aware, has been able to fill completely the well cavity around the liner with a fully settled and compacted gravel pack which eliminates sand entry and does not eventually plug the liner perforations or screen section. The result has been that erosion of the formation sands begins at' the location where4 the well cavity is not completely gravel filled. Once started, the erosion process accelerates and sloughing o f formation intoY the well cavity occurs. The formation sand plugsl up the gravel openings and the liner screen section apertures, reducing the number of apertures available to pass the well' Il uid, and this causes localized increased incoming velocity ofthe fluid which leads to more pronounced. erosion, resulting in high production costs, low ultimate recovery and possible well failure.v (Itwill be understood that the word "sands as used herein includes sands and shales and other formation detritus.)

An impor-tent feature ef. my invention relates te the manner 0f installing gravel Particles. inte e eevitv around. the liner in order tov securev maximum filling and max imum settling action. Heretofore, it h as been generally thought necessary to have the size of the gravel particles larger than the size of the screening perforations of the liner in Order te prevent, the gravel particles tem passies inwardly through the liner perforations, and` accordingly gravel packing techniques as actually practiced have emrleyed, gravel partiel/es which. Werelerser than `the perforations.` However, I have found that it is possible to instell, and Settle steve! peltielee in the Well Cavity @relied the perforated liner by' a novel method, and providing gravel particles for the pack in which all or the greater percent are small enough to pass through the liner perforations, 'but which are effectively and stably bridged against doing so, and thereby secure a pack which will stop formation sandy particles fromentering the pack to any harmful extent.

Other related features, objects and advantages will aip-Y pear hereinafter. Irl-,the accompanying drawings is shown only so much of the well and apparatusy necessary to illu'strate the carrying outA of my invention, to those skilled inthe art. l j

Fig.- l is asectional elevation ofy an oil well passing through various strata including the'oil-bearing sandsv and with the Well bore` enlarged below the cemented-off casing to form the gravel cavity, and with the perforated liner screen section in place and seated at the bottom of the Cavitye t Fig. 2 is a sectional elevation on a largerl scale showing fe AICC details of the apparatus for carrying out my improved gravel packing method.

Fig. 3 is a vView similar to that of Fig. 2 showing the gravel packing apparatus connected to the upper end of the perforated liner.

Fig. 4 is an enlarged cross sectional view of Fig. 3 taken on the line 4 4 thereof.

Fig. 5 is an enlarged cross sectional view of Fig. 3 taken on the line 5-5 thereof.

Fig. 6 is a view similar to that of Fig. 1- but showing the operation of a bailer for use in settling the gravel particles in the well cavity around the perforated liner.

In further detail, the drawings show at 10 the casing within the well bore 11 cemented off at 13 toY form a casing shoe which extends for a distance up the Vannular space 14 from the upper end of the enlarged gravel cavity 17, all as well understood in the art.

I ust below the cemented-off casing the continuing well bore is enlarged as by a rotary or other wall scraper, well known in the art, to a diameter preferably about 11/2 to 2 times the well bore, to form the cavity to receive the gravel. pack around a perforated liner or screen 18 when in position therein. This enlarged cavity extends downf Ward from a point above the oil sands stratum 15 or strata to a point below the lowermost as indicated in Fig. lV where the screen liner restson the bottom 19 of the cavity. The liner is closed at its lower end.

The perforated liner or screen pipe 18 is lowered into place on the lower end of a drill pipe string 20, the. upper end of the liner being provided with a lefthand screw-y thread 21.

As shown in Figure 2, a special connection piece 22 is provided with a lefthand thread 23 to receive the lefthand thread 21 on the liner 18. This connection piece 22 carries a downwardly extending tube or wash pipe 24 which is connected to it by threads 25. The lower end of this wash pipe is open, as shown at 26, and is preferably cut olf at a forty-live degree angle. This wash pipe extends downwardly into the perforated liner 18 and terminatesy near the lower end of the liner. The lower end of the. liner is closed as indicated.

The connection piece 22 is provided withy alost motion connection tothe drill string Z0. This lost motion connection is provided by the telescoping Vparts 27 and 28,. The part 27 is attached toV the drill string 20, and has a noncircular portion 30- which projects into. a noncircular bore 31 provided in the cap 28. Threads 33 connect theL cap with the part 22. The lower end of the part 2,'7V carries an enlargement 34 which travels between the abutments 35 and 36. The parts just described provide a.

connection between the drill string 20. and the liner 18 which permits limited axial movement between them but which prevents relative rotary movement. A resilient seal ring 22a on the member 22 engages the interior of theand also includes a passage 38 which establishes` com-V munication between the interior of the drill string 2t) and Ithe annular space` 41. below the sealing ring 22a to the. gravel cavity 17. f i Y After the screen pipe or liner 18 is run into, the well suspended on the lower end of theA connection piece. 2 2 to a position extending above the cavity 17 as shown in Fig. 3., fluid is pumped and circulated down through the.l

drill pipe string 20 and through the passage 38 and out into the gravel cavity 17, returning inwardly through the Aliner perforations 39, and upward through wash pipe .24

and annular space 40 withinthe casing 10 and out of the top to 'wash out loose matter from the cavity. Then gravel particles, which are screened or classified to substantially the same size and of which all or the greater percent are small enough to pass through the liner apertures 39 are then introduced into the [luid pump stream, by means well known in the art, and passing downwardly through the drill pipe string 20 and the suspended gravel passes through the side passage 38, through the lower annular space 41 below the seal 22a and into the upper end of the gravel cavity 17. The amount of `gravel particles so introduced is calculated from the known size and length of the cavity 17 and from the length of the overlap zone between the liner 18 and casing 10, and which zone should be long enough to hold a reserve amount of gravel to maintain the cavity full at all times after the pack has been nally settled.

The size of the gravel particles will, of course, depend on the size of the formation sands of the particular well which must be kept from ltering through the gravel pack, and I have found that it is possible to use gravel particles which are small enough to pass through the liner perforations because, by my method, they can be made to bridge over the perforations during my manner of placing the gravel in the well and this assures maximum opening area of the available perforations. The gravel particles which are so introduced into the upper end of the cavity 17 tend to scour the walls of the cavity and to rearrange themselves into the most compact space While they settle Within the cavity. After the gravel has initially lled the cavity, I prefer to lift up- Wardly on the drill string 20 for a distance suflcient to raise the liner 18 off the bottom for a foot or so. The liner may be yraised and lowered several times through this short distance in order further to agitate and densify the gravel around it and assist in the settling action. The liquid which is used to carry the gravel into place continues to enter the upper end of the cavity with its suspended gravel and the liquid escapes inwardly through the liner perforations 39 and out through wash pipe 24. The circulating liquid may be oil or Water though I prefer salt Water if ocean water is available.

Some of the gravel particles also pass into the interior of the liner 18 through its perforations and substantially all of the sand, sil't, mud and other foreign material near the bottom of the well also passes inwardly through the perforations 39. Y

It should be noted that while the perforations of screen openings 39 of the liner are larger than the main body of the gravel particles throughout the length of the cavity 17, the perforations in the liner above the cavity, i.e. in the casing-liner overlap space 41 are preferably a trie smaller than the main body of the gravel particles, as the gravel in this extra long annular space last introduced is a less compacted gravel feeder column to take care of any slow settling of the pack after long service.

The gravel particles and foreign material which enter the liner during the cavity filling operations are carried in the fast moving fluid stream into the open lower end of the wash pipe 24 and pass upward and out of the top of the well in the casing 10. When the circulating pressure builds up because of lling of the liner and casing overlap zone 41 following the complete filling of the cavity 17, the pumps are stopped and the drill string 20 is turned in a direction to release the lefthand threads 21 and 23 as shown in Fig. 2, the liner 18 being prevented from rotating by means of the frictional resistance offered by the gravel and the centering bow springs 42 of the vcentralizers 43. It will be understood that any desired number of centralizers may be employed both within the overlap zone, such as the usual fins (not shown), and within the cavity 17. After release of the lefthand threads 21 and 23, the drill string- 20, connection piece 22 and the wash pipe 24, are Withdrawn up- Wardly and removed from the well.

A bailer 44 is then run into the well on a wire line 45 Y space.

4 4 and enters the interior of the liner 18, as shown in Fig. 6. This bailer is conventional in design and has a reasonably close running t with the interior of the liner 18. The upper end 46 of the bailer is open and the lower end is closed by a dart valve assembly 47. This assembly opens when the lower end thereof strikes an obstruction and the size of the opening, as so produced, is large enough to admit gravel. The bailer is lowered until the valve assembly 47 strikes bottom or engages any material remaining in the lower end of the liner and opens to admit it, and closes when pulled up.

The bailer 44 is then lifted slowly at rst and then rapidly to reduce the pressure inside the liner and below the bailer and this operation is repeated several times. The swabbing action and reduction in pressure causes a suction and thereby additional gravel particles to enter the liner through the perforations 39 and thus together with the vibration involved causes the settling and rearrangement of the gravel particles to densify the gravel pack in the cavity 17 and bridge the liner perforations. The bailer is then raised to the surface and emptied of any contents. This is repeated several times. The well is of course always full of liquid.

The drill string 20, connection piece 22 and Wash pipe 24 are again lowered into the well and the wash pipe into the liner, and plain lluid is pumped down and rapidly circulated as shown by the arrows in Fig. 2. Gravel particles and foreign material are thereby removed or jetted from the interior of the liner 18 through the wash pipe 24. The slant cut lower end of the wash pipe is important to prevent plugging. The member 22 is then connected to the upper end of the liner 18 by means of the left hand threads 21 and 23. Additional suspended gravel is then pumped through the interior of the drill pipe string 20 and is carried into the cavity 17 in the stream of liquid: Although suflicient gravel was initially introduced to completely lill the cavity 17 and overlap space 41, the swabbing, suction, and surging action of the bailer will have reduced the level of the gravel some what so that additional gravel is accommodated. The drill pipe string 20 may again be raised and lowered repeatedly to apply a tapping, jarring and pounding action by means of the enlargement 34 and abutments 35 and 36 of the lost motion connection and to vibrate the liner 18 to further settle the gravel particles into the most compact and stabilized form, so that notwithstanding the particles are mostly smaller than the width of screen openings or slots they will have been bridged and will not come through to any harmful extent.

The drill string 20, connection piece 22 and wash pipe 24 are again withdrawn from the well and the bailer again operated in the manner as described to further insure the nal settling of the pack and removal of free material.

If jetting out the loose material is also used, a high pressure water or air pipe with upwardly directed iets at its lower end is lowered into the screen and operated as well understood in the art.

'I'he foregoing explained steps of introducing gravel and of bailing the interior of the liner and tapping by the lost motion device are repeated in turn until no more gravel can be introduced into the well. By that time, each of the perforations 39 n the liner 18 has been bridged over by the gravel and the cavity 17 and the long overlap space 41 completely full. The gravel pack around the `liner has been fully settled and densiiied with the individual gravel particles occupying the most compact plugged by gravel particles partially filling the perforations, as is the case in conventional gravel pack installations, but have become openly bridged with free interstices. The size of the cavity I17 should be such that the v area of the interface between the gravel pack and the wellV formation is large enough to reduce the inward 'flowof well `fluid velocities below the critical value at which Moreover, the individual perforations are notV erosion would take place and so that erosion of sand or other solids from the well formation does not commence. The diameter to which the gravel cavity is enlarged is also quite critical, for if too small the formation sands may work through, and if too large there will be difficulty in completely filling it perfectly and maintaining it so. Therefore, the size ratio of cavity to well bore yas given, supra, is important. (Column 2, lines 18-21.)

The following gures are given as a successful example of a particular well which was gravel packed in accordance with my invention above described.

The well is identified as Belridge No. 6 at South Belridge Oil Fields, Kern County, California. The total depth of the well is 1,140 feet. Well casing, SS/s inches in diameter, is cemented at 1,003 feet in a hole 11 inches in diameter. A 6% inch liner extended from the 915 foot level to the bottom of the well. The well cavity below the cemented off casing was scraped and enlarged to 19 inches in diameter before the liner was placed in position. Initially 345 cubic feet of gravel was introduced into the well and 60 cubic feet of gravel was returned to the surface. Four inch drill pipe was used to carry the stream of liquid and gravel particles. The gravel was rounded rather than angular and varied in size from 0.065 to 0.078 inch maximum dimension. The liner perforations from the 915 foot level to the 1,005 level were 0.060 inch in Width. The remaining liner perforations from the 1,005 foot level to the lower end of the liner were 0.110 inch wide.

After the rst hailing operation, the drill pipe was reinserted into the well and connected to the liner. An additional 53 cubic feet of gravel particles was introduced. After withdrawal of the drill string, the bailer was again run into the well and operated on a wire line. Subsequently, only 8 cubic feet of gravel could be removed. On the third operation of introducing gravel particles, only 1 cubic foot of gravel could be installed. The remainder was circulated out of the Well. The gravel cavity 'was then completely full of gravel and the gravel was settled to occupy the least amount of space. The Well has been on production for suicient time to demonstrate that its rate of production is consistently greater than similar adjacent wells gravel packed by conventional methods, and that it produces substantially no sand, whereas the adjacent wells have chronic trouble due to sand production.

A well, gravel packed in accordance with my method, is ideally suited to water ooding operations to perform either as a water injection well or as a recovery Well producing oil in response to water ldrive. Sanding difculties ordinarily increase as the percentage cut of water increases in the well production but the improved gravel pack which is produced by my method is effective to eliminate harmful sand entry, even when the liquid passing through the sand is predominantly water.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth but feel that my invention is of the full scope of my appended claims.

I therefore claim:

1. Gravel packing apparatus for use on a pipe string within a well casing for installing gravel in a well cavity around a perforated liner, comprising, in combination: a member having a releasable connection for engagement with the upper end of the liner and having means thereon for establishing a seal with the interior of the casing, `a wash pipe on the member adapted to project downwardly into the interior of the liner and having an open lower end cut at an angle, a rst passage on the member between the wash pipe and the space outside the member and above the seal means, means including a hollow element on the member for connecting the member to the pipe string, and a second passage on the member between the hollow element and the space outside the member and below the seal means, whereby fluid may pass downward from the pipe string through the hollow element and second passage into ,the well cavity, and then through the liner perforations and upward through the wash pipe, first passage, and in to the casing outside the pipe string below said hollow element, said hollow element including an axially slidable fluid-tight portion and abutments to form a lost motion pounding or jarring member for the perforated liner below.

2,. Gravel packing apparatus for use on a pipe string within a Well casing for installing gravel in a well cavity around a perforated liner, comprising, in combination: a member having a releasable threaded connection with the upper endV or" the liner and having means thereon for establishing a seal with the interior of the casing, a hollow open-ended wash pipe on the member adapted to project downwardly into the interior of the liner, a first passage on the member between the wash pipe and the space outside the member and above the seal means, means including a hollow element for connecting the member t0 the pipe String, the hollow ,element having a ,nonrotatable .axially ,Slidable 0r 10st motion pounding cr jarring Connection with Said member, and a Second passage on the member between the hollow element and .the Spa@ outside .the member and belcw the seal means, whereby `fluid may pass downward from ,the pipe string through the hollow element Iand second passage into the well cavity,-and then through the liner perforations and upward through the wash pipe, .first passage, and .into the casing outside the pipe string.

3. A gravel pack encircling a perforated screen pipe positioned in a well cavity, the pack completely filling the cavity about the outer sides of the screen pipe and composed mostly of previously classified but compacted gravel particles each of a size which can pass through the screen `apertures but are in stably bridged arrangement across the apertures.

4. A gravel pack encircling a perforated screen pipe positioned in a well cavity, the pack completely filling the cavity about the outer sides of the screen pipe and composed mostly of previously classified but compacted gravel particles each of a size which can pass through the screen apertures but are in stably bridged arrangement across the apertures, said cavity being surmounted by a feed column of said gravel particles to maintain the cavity full is settling.

5. In a well gravel pack as set out in claim 4, the screen pipe extending upward into the feed column and provided along this area only with screen apertures smaller than the gravel particles to prevent the feed column gravel from passing therethrough.

6. An improved method of gravel packing a well cavity enlarged about a screen pipe in the cavity, which comprises introducing gravel by uid flow from above into the cavity about the screen pipe to iill the cavity, said gravel having been classified to a particle size where substantially all of the particles can pass through the apertures of the screen pipe, and applying mechanical shocks and vibrations to the screen pipe, washing out the loose and dislodged particles upwardly from within the screen pipe `and out of the well, while introducing more of the classified gravel to keep the cavity full, until settling of the gravel particles of the pack into stable arrangement and particularly bridged across the Iscreen apertures, has been effected.

7. In a method of gravel packing a well as set out in claim 6, the further step of overiilling the cavity with the classified gravel to provide a make-up storage column of gravel about an upward tubular extension of the screen pipe spaced in the well bore above the enlarged cavity.

8. An improved method of gravel packing a well cavity enlarged about a screen pipe in the cavity, which comprises introducing gravel by fluid flow from above into the cavity about the screen pipe to till the cavity, said gravel having been classied to a particle size where the major portion of the particles can pass through the apertures of the screen pipe, and repeatedly applying mechanical shocks and vibrations to the screen pipe and repeatedly Washing out the loose `and rdislodged particles upwardly from within the screen pipe and out of the well, while repeatedly introducing more of the classified gravel to keep the cavity full, until substantially no more can be added or removed by further washing and until settling of the gravel particles of the pack into stable arrangement and particularly bridged across the screen apertures has been effected.

9. An improved method of gravel packing a well cavity enlarged about a screen pipe in the cavity, which comprises introducing gravel by fluid ow from above into the cavity about the screen pipe to ll the cavity, said gravel having been classiiied to a particle size where the major portion of the particles can pass through the apertures of the screen pipe, and repeatedly applying mechanical shocks and vibrations to the gravel pack adjacent the screen pipe, by lifting and lowering the screen pipe at intervals, and also jarring the pipe string, and bailing, and washing the loose and dislodged particles from within the screen pipe upward and out through a wash pipe until settling of the gravel particles of the pack into stable arrangement and bridging of the particles across the screen apertures has been eiected.

`10. An improved method of gravel packing a well 8 t s e cavity enlarged about a screenV pipe in the cavity, which comprises Vintroducing gravel by fluid ow from above into the cavity about the screen pipe to till the cavity, said gravel having been classied to a particle size Where the major portion of the particles can pass throughY the apertures of the screen pipe, and repeatedly applying mechanical shocks and vibrations to the Vgravel pack adjacent the screen pipe, by lifting and lowering the screen pipe at intervals, and also vjarring the iluid string, repeatedly swabbing the interior of the lscreen pipe with a bailer and creating a suction eiect below the bailer by rapidly moving it upward to cause allV unstable particles of gravel to enter the screen pipe, hailing them out, and jet Washing out the loose and dislodged particles within the screen pipe upward through a Wash pipe and out, all while maintaining the cavity completely full of gravel, until settling of the gravel particles of the pack into stable arrangement, particularly bridged across the screen apertures, has been effected.

References Cited in thele of this patent Y UNITED STATES PATENTS 2,014,770 Layne Sept. 17, 1935 2,207,184 White July 9, 1940 2,216,037 Layne sept. 24, 1940 2,597,554 West May 20, 1952 

